If you are not registered in a state, you may not have the right to sue, which can limit your ability to collect debts and pursue your rights as a business.
If the state in which you do business requires out-of-state companies to register as foreign corporations and you neglect to do so, you may have to pay weighty penalties.
If you are doing business in your home state and you have not qualified as a foreign corporation in that state, you may be unable to pursue legal rights until you qualify. By that time, the statute of limitations may have run out.
Don't be daunted by the foreign filing process. As with becoming incorporated, it's simply a matter of correctly filling out the appropriate forms and paying the filing fees.